Fetlock joint receives an in-depth analysis

Orthopedic surgeon says preserving cartilage matters most
Published on January 18, 2010
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By Malinda Larkin

The fetlock joint is the joint that makes a horse a horse, of course, of course. 

This pivotal joint was the focus of the Frank J. Milne State-of-the-Art Lecture Dec. 7, 2009, during the American Association of Equine Practitioners 55th Annual Convention. Dr. Larry R. Bramlage, an orthopedic surgeon and partner at the Rood & Riddle Equine Hospital in Lexington, Ky., and diplomate of the American College of Veterinary Surgeons, delivered the lecture.   

 "An orthopedic surgeon must be able to think like a bone and feel
like a joint simultaneously," Dr. Larry R. Bramlage said during the
 2009 Frank J. Milne State-of-the-Art Lecture.

His talk, "Operative orthopedics of the fetlock joint of the horse: Traumatic and developmental diseases of the equine fetlock joint" addressed the causes of fetlock joint diseases and provided information on surgical concepts and treatments for these conditions. Dr. Bramlage also discussed techniques for eliminating joint pain through surgical arthrodesis. 

Dr. Bramlage said when he considered what he worked on the most in his practice, the fetlock joint first came to mind. He found that of the 10,888 surgeries he has performed on horses in the past decade, 4,069 of them involved the fetlock joint, about 37 percent of his caseload. 

He compared the joint's construction to a suspension bridge in that none of the members is able to carry the load unless supported by a suspension band. It is a shock absorber, energy storage system, and stabilizer. An equine veterinarian's prime directive is to keep it from degenerating, he said. 

Often what equine veterinarians see in the fetlock joint is degenerative arthritis secondary to a developmental abnormality or traumatic injury. These conditions shed debris into the joint, which, coupled with the joint's attempt to heal the insult, fuels much of the inflammatory cycle that results in secondary degenerative arthritis. 

What practitioners need to be aware of is misdiagnosing joint inflammation, Dr. Bramlage cautioned. 

"Degenerative joint disease has sometimes erroneously become a catchall for any change seen on radiographs," he said. "Most of the diseases in the fetlock joint do not fall in this category until late in the disease." 

Use precipitates the disease, and exercise intensity dictates the progression rate. High intensity activity causes rapid, intense signs, Dr. Bramlage said. This means a veterinarian may be able to catch it earlier on if he or she is paying attention. On the other hand, lower intensity activity results in insidious low-level signs and lameness that remains subclinical. Nonetheless, once the horse reaches the same total amount of debris shedding, the condition of the joint will be similar, Dr. Bramlage said. 

Each diagnosis of potentially damaging traumatic fragmentation or developmental bone malformation must be evaluated in light of the long-term expectations for the horse's performance and the ability to replace the horse, including the economic realities. 

What that comes down to, then, is often surgical versus medical treatment. Early surgical treatment requires an upfront expense but with the prospect of permanently solving the condition. Dr. Bramlage estimated that the cost of surgery is roughly equal to the cost of two to 10 injections of interleukin receptor antagonist protein, or IRAP. 

Medical treatment, on the other hand, may be able to relieve clinical signs or interrupt the biologic processes associated with joint inflammation, but will not stop the physical debris shedding, which continually takes its toll on the hyaline cartilage, he said. In fact, medications can be abused if they are used to cover up a physical problem that continues to damage the joint. 

"The decision to do surgery is no longer a last resort," Dr. Bramlage said. "The worst choice is to 'maintain' the joint with injections and go to surgery when you have to. This guarantees the most cost." 

A real breakthrough will occur when researchers can re-create anchorage tissue or bone, Dr. Bramlage said. Until then, he thinks microfracture surgery has a lot of potential to help cartilage reattach to bone. 

His conclusion is that no surgical technique can be depended on to replace lost articular cartilage in horses, or people, for that matter. The role of treatment is to preserve the joint in its current condition. Surgery, he said, prevents degenerative arthritis and can have the most effect in stabilizing the bone and preserving the cartilage and synovial lining.